JP3168613B2 - Magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic tape and a magnetic disk, and more particularly to a magnetic recording medium using a quaternary ammonium salt of perfluoropolyether having a terminal carboxyl group as a lubricant. It relates to a recording medium.

[0002]

2. Description of the Related Art For example, in the case of a so-called metal thin film type magnetic recording medium in which a ferromagnetic metal material is deposited on a non-magnetic support by a method such as vapor deposition and the magnetic layer is used as a magnetic layer, the smoothness of the magnetic layer surface is reduced. Since it is extremely good, a substantial contact area with a sliding member such as a magnetic head or a guide roller is large, and therefore, the friction coefficient is large, and an adhesion phenomenon (so-called sticking) is likely to occur. There are many problems such as chipping.

[0003] In order to solve these problems, use of various lubricants has been studied. Conventionally, higher fatty acids and esters thereof have been applied to the magnetic layer of the magnetic recording medium by top coating. Attempts have been made to reduce the coefficient of friction. Incidentally, lubricants used for magnetic recording media are required to have extremely strict characteristics due to their properties, and it is difficult for conventional lubricants to cope with them.

[0004] That is, the lubricant used for the magnetic recording medium is (1) to have excellent low-temperature characteristics so as to ensure a predetermined lubricating effect when used in a cold region. (2) Since spacing with the magnetic head becomes a problem,
It must be able to be applied very thinly, and in that case it should also exhibit sufficient lubrication properties. (3) Long-term use or long-term use, and the lubrication effect is maintained. Etc. are required.

However, conventionally used higher fatty acids and esters thereof are frozen and solidified under low-temperature conditions such as 0 ° C. or lower, so that the function as a lubricant is impaired or the durability for a long time is deteriorated. Tend to lack.

[0006]

As described above, in the field of magnetic recording media, practical properties such as running properties and durability remain unsatisfactory due to insufficient capacity of the lubricant used. . Therefore, the problem to be solved by the present invention is:
An object of the present invention is to provide a magnetic recording medium that maintains excellent lubricity under various use conditions, maintains a lubricating effect for a long time, and is excellent in running properties, wear resistance, durability, and the like.

[0007]

Means for Solving the Problems According to the present invention, as a result of diligent studies to solve this problem, a quaternary ammonium salt having a carboxyl group at a terminal is found to be suitable for solving this problem. Thus, the present invention has been completed. That is, the magnetic recording medium of the present invention is a magnetic recording medium in which at least a metal magnetic thin film is formed as a magnetic layer on a non-magnetic support,

[0008]

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Or,

[0010]

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Here, Rf represents a perfluoropolyether group. R ₁ , R ₂ , R ₃ and R ₄ represent the same or different hydrocarbons. Characterized by having a quaternary ammonium salt compound of perfluoropolyether having a carboxyl group at the terminal represented by

That is, according to the present invention, good durability can be obtained even when used under severe conditions, such as high temperature, high humidity, or low temperature, low humidity, by coating on the surface of a thin film magnetic recording medium such as a vapor-deposited tape. Moreover, its characteristics do not deteriorate. These compounds can be obtained, for example, by mixing a metal salt of perfluoropolyether having a carboxyl group (such as a sodium salt) and a quaternary ammonium salt (such as a chloride or a sulfate) and extracting the mixture with an organic solvent. it can.

The quaternary ammonium salt of the perfluoropolyether having a carboxyl group at the terminal as the quaternary ammonium salt of the present invention is not limited by molecular weight, branched structure, unsaturated bond, isomer structure and alicyclic structure. You can choose. Specifically, Table 1 shows the structure. Perfluoropolyether can be used in any of monofunctional and polyfunctional.For example, monofunctional examples include F (CF2CF2CF20) n
CF2CF2COOH or

[0014]

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The polyfunctional perfluoropolyether includes, but is not limited to, HOOCCF2 (OCF2CF2) p (OCF2) qOCF2COOH and the like. As the quaternary amine salt compound, a commercially available product or a synthetic product was used. Here, l, m, n, in the chemical structural formula of the above perfluoropolyether,
p and q each represent an integer of 1 or more. The molecular weight is not particularly limited, but is preferably about 600 to 5,000.
If the molecular weight is too large, the effect of the terminal group is small, and if it is too small, the effect of fluorine is weakened. In the case of an amine, it is preferable that at least one alkyl group has 10 or more carbon atoms.

The magnetic recording medium of the present invention has a quaternary ammonium salt of perfluoropolyether having a carboxyl group at a terminal as a lubricant. Here, as the magnetic recording medium to which the present invention is applied, it is possible to apply the present invention to a so-called metal thin film type magnetic recording medium in which a magnetic coating film is formed as a magnetic layer on a nonmagnetic support surface by a method such as vapor deposition. It is possible. Further, this metal thin film type magnetic recording medium can be applied to a magnetic recording medium having a configuration in which an underlayer is interposed between a nonmagnetic support and a magnetic layer.

In this case, the non-magnetic support of the metal thin film type magnetic recording medium and the metal magnetic thin film which can be applied are not limited at all, and any conventionally known ones can be used. For example, the same non-magnetic support as the above-mentioned coating type magnetic recording medium can be used. In this case, when a rigid substrate such as an Al alloy plate or a glass plate is used for the non-magnetic support, an oxide film such as alumite treatment or a Ni-P film is formed on the substrate surface to harden the surface. You may make it.

The metal magnetic thin film is formed as a continuous film by a PVD technique such as plating, sputtering, or vacuum evaporation, and is made of a metal such as Fe, Co, Ni, or Co-Ni.
Alloy, Co-Pt alloy, Fe-Co-Ni alloy,
Fe-Co alloy, Fe-Ni alloy, Fe-Ni-B
Alloy, Fe-Co-B alloy, Fe-Co-Ni-B
In-plane magnetization recording metal magnetic film made of a system alloy or the like, Co-Cr
A system alloy thin film is exemplified.

In particular, in the case of an in-plane magnetization recording metal magnetic thin film,
Bi, Sb, Pb, Sn, Ga,
A base layer of a low-melting non-magnetic material such as In, Ge, or Ti is formed, and a metal magnetic material is vapor-deposited or sputtered from a vertical direction to diffuse the low-melting non-magnetic material into the metal magnetic thin film. May be eliminated to ensure in-plane isotropy and improve coercivity.

When a hard disk is used, a carbon film, a diamond-like or amorphous carbon film, a chromium oxide film, a SiO
A hard protective film such as _two films may be formed. Such a metal thin-film type magnetic recording medium is provided with a quaternary ammonium salt of perfluoropolyether having a carboxyl group at the terminal by a lubricant layer on the surface of the metal magnetic thin film or the surface of the protective film. There is a method of coating. In this case, the coating amount of the quaternary ammonium salt compound of perfluoropolyether terminated with a carboxyl group, is preferably a 0.5-100 mg / m ^2, more preferably 1-20 mg / m ² .

The above quaternary ammonium salt compound of perfluoropolyether having a carboxyl group at the terminal is
It may be used alone as a lubricant for a magnetic recording medium, or may be used in combination with a conventionally known lubricant. Further, in order to cope with more severe conditions and maintain the lubricating effect, an extreme pressure agent may be used at a mixing ratio of about 30: 70-70: 30 by weight.

In the boundary lubrication region, the extreme pressure agent reacts with the metal surface due to the frictional heat generated when the metal contact occurs partially to form a reaction product, thereby producing friction,
It exerts an anti-wear effect, and any of a phosphorus-based extreme pressure agent, a sulfur-based extreme pressure agent, a halogen-based extreme pressure agent, an organometallic extreme pressure agent, a composite extreme pressure agent, and the like can be used. Further, in addition to the above-mentioned lubricant and extreme pressure agent, if necessary, a rust preventive may be used in combination.

Any rust preventive can be used as long as it is generally used as a rust preventive for this type of magnetic recording medium, such as phenols, naphthols, quinones, and the like.
Examples include a heterocyclic compound containing a nitrogen atom, a heterocyclic compound containing an oxygen atom, and a heterocyclic compound containing a sulfur atom. Incidentally, in the above-described metal thin film type magnetic recording medium, a back coat layer, an underlayer, and the like may be formed as necessary in addition to the metal magnetic thin film as the magnetic layer.

For example, the back coat layer is formed by adding a carbon-based fine powder for imparting conductivity or an inorganic pigment for controlling the surface roughness to the same resin binder as the magnetic coating film, and is formed by coating. is there. In the present invention, the back coat layer may contain the above-mentioned quaternary ammonium salt compound of perfluoropolyether having a carboxyl group at a terminal as a lubricant internally or by a top coat. Alternatively, various combinations are possible, such as internal addition and top coating as a quaternary ammonium salt compound of a perfluoropolyether having a carboxyl group at a terminal in any of a magnetic coating film, a metal magnetic coating film and a back coat layer. .

[0025]

The quaternary ammonium salt compound of perfluoropolyether having a carboxyl group at the terminal exerts a good lubricating action and reduces the friction coefficient. Further, this lubricating action is not impaired even under severe conditions such as low temperature. Therefore, the magnetic recording medium using the quaternary ammonium salt compound of a perfluoropolyether having a terminal carboxyl group as a lubricant has the above-mentioned properties. The effect improves runnability and improves durability.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described, but it goes without saying that the present invention is not limited to these embodiments. As described above, Table 1 shows the synthesized quaternary ammonium salt compounds of perfluoropolyether having a carboxyl group at the terminal.

Using the composites shown in Table 1, the following magnetic recording media were prepared. An embodiment applied to a metal thin film type magnetic recording medium (evaporated tape) will be described. Example 1 Co was applied on a polyethylene terephthalate film having a thickness of 14 μm by oblique deposition to form a ferromagnetic metal thin film having a thickness of 200 nm. Next, a solution obtained by dissolving Compound 1 in Table 1 in a mixed solvent of Freon and ethanol was applied to the surface of the metal magnetic thin film so that the application amount was 5 mg / m ^2, and 8 mm
The sample tape was cut to a width.

-Examples 2 to 14- In Example 1, the same method as in Example 1 was used, except that Synthetic 1 in Table 1 used as a lubricant was changed to Synthetic 2-Synthetic 14. To prepare a sample tape. For each sample tape prepared as described above, the temperature was 25 ° C and the humidity was
The coefficient of friction, still durability and shuttle durability were measured at 60%, at a temperature of -5 ° C, at a temperature of 40 ° C, and at a humidity of 80%. Still durability is-
The decay time up to 3 dB was evaluated. Shuttle durability was evaluated by the number of shuttles performed until the output decreased by 3 dB after running the shuttle for 2 minutes each time.

As comparative examples, measurements were also made on a plank tape using no lubricant at all and a case using perfluoropolyether having a carboxyl group at a terminal alone as a lubricant. Table 2 shows the results. As is clear from Table 2, by using a perfluoropolyether having a carboxyl group as a lubricant as a quaternary ammonium salt compound of a perfluoropolyether having a carboxyl group as compared with a case where a perfluoropolyether having a carboxyl group is used alone, Coefficient of friction, still durability, shuttle durability, etc.
Very good results were obtained without deterioration under various conditions.

[0030]

As is apparent from the above description, the magnetic recording medium of the present invention uses a quaternary ammonium salt compound of perfluoropolyether having a carboxyl group at the end having extremely excellent lubricity as a lubricant. Because it possesses, it can maintain lubricity under any use conditions,
Further, the lubricity can be maintained for a long time. Therefore, the magnetic recording medium of the present invention has excellent running properties, wear resistance and durability.

[0031]

[Table 1]

[0032]

[Table 2]

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G11B 5/71 C10M 105/50-105/66 C10N 30:08 C10N 40:18

Claims (1)

(57) [Claims] At least a metal magnetic thin film is provided on a nonmagnetic support.
A magnetic recording medium having a film as a magnetic layer,
A magnetic recording medium having a quaternary ammonium salt of perfluoropolyether having a carboxyl group represented by the following general formula on its surface . Embedded image Or Here, Rf represents a perfluoropolyether group. R ₁
, R ₂ , R ₃ and R ₄ represent the same or different hydrocarbons.